In recent years, along with the prevalence of networks, not only personal computers but also various devices such as mobile phones, electronic devices, and the like can be connected to networks. Environments used by mutually linking electronic devices and the like extend not only to office use but also home use since home electric appliances and other electric appliances which are solely used so far are connected to networks.
Easy connections and easy settings of various devices to be connected to networks are required above all.
As one of network techniques that can meet such requirements, a technique called Universal Plug and Play (to be abbreviated as UPnP hereinafter) is available. The UPnP is characterized in that it can apply a plug and play function to devices connected to the network, no driver software or the like need be installed, and it does not depend on the types of OSs (operating systems) running on devices.
Using the UPnP, the device can automatically do all of functions: to enter a network and dynamically acquire an IP address, to notify the self functions, to acquire the presence and functions of another device, and so forth, and to allow true zero network settings. Furthermore, the devices can directly communicate with each other, and form a peer-to-peer network.
The detailed specification of the UPnP is described in Universal Plug and Play Device Architecture Version 1.0.
However, with the above prior art, the UPnP or the like which can dynamically acquire an IP address and can notify the self functions cannot discover and control, e.g., device across the Internet, i.e., it cannot use a device which does not belong to the same subnet.